The present invention relates to a scanner unit installed in, for example, a copy machine.
In general, a copy machine is provided with a scanner unit for scanning an image of a document to be copied. The scanner unit has a substantially horizontal glass document table for mounting a document thereon.
Below the document glass table, first and second carriages are provided, which extend along the glass document table from the front-side of the machine to the rear-side, i.e. in a main scanning direction. The first carriage includes a first frame provided with a lamp for illuminating a document placed on the glass document table, a reflector for reflecting the light of the lamp onto the surface of the document, and a first mirror for changing the direction of the light reflected from the document by 90°. The second carriage includes a second frame provided with a second mirror for changing the direction of the light reflected from the first mirror by 90°, and a third mirror for changing the direction of the light reflected from the second mirror by 90°. Light reflected from the third mirror is guided to a light receiving element via a condenser.
The casing of the scanner unit contains, at its front and rear sides, two rails that support the front-side and rear-side ends of the first frame of the first carriage so that the frame can slide, and two rails that support the front-side and rear-side ends of the second frame of the second carriage so that the frame can slide. Further, the front-side end of the first carriage is connected to the front-side end of the second carriage by means of a wire tensioned therebetween via a plurality of pulleys, while the rear-side end of the first carriage is connected to the rear-side end of the second carriage by means of a wire tensioned therebetween via a plurality of pulleys. When running the wires, the first carriage slides along corresponding rails at a predetermined speed in a sub-scanning direction, and the second carriage is driven by the first carriage to slide at half the speed of the first carriage along corresponding rails in the sub-scanning direction.
When packing and shipping the copy machine equipped with the scanner unit, it is necessary to fix the frames of the first and second carriages to the casing of the scanner unit, since the first and second carriages are mounted on the rails in an unstable manner. If the first and second carriages are not fixed, each carriage may touch a peripheral component, thereby deforming its frame or damaging an optical member such as a lamp or a mirror.
In light of the above, the copy machine is shipped in a state as shown in FIG. 7, in which the second frame 144 of the second carriage is screwed to a casing wall 132L of the scanner unit, and the front-side and rear-side ends of the first frame 143 of the first carriage are screwed to casing walls 132f and 132r. 
When, for example, screwing the rear-side end 143r of the first frame 143 of the first carriage to the casing wall 132r as shown in FIG. 8, the rear-side end 143r of the first frame 143 is screwed to a plate section 201 projecting from the casing wall 132r. In this case, a screw 203 is inserted through a hole 202 formed in the plate section 201, and a front end portion 205 of the screw 203 is inserted into a hole 204 formed in a end portion 143r of the first frame. At this time, a threaded portion 206 provided at the proximal end side of the screw 203 is screwed with the hole 202 of the plate section 201, thereby fixing the first frame 143 to the casing 132.
However, when screwing the opposite ends of the first frame to the casing as described above, a delicate job of inserting the screw 205, through the very small hole 202 of the plate section 201, into the much smaller hole 204 of the first frame is required. Since it is difficult to detect the hole 204 itself and hence to insert the screw 203 into the two holes 202 and 204, a lot of time and effort is necessary for fixing the first frame.